Electronic calculators, microprocessors, and other information processing devices frequently employ bus circuits to transfer information from one register or storage device to another.
One method of accomplishing this information transfer employs stray capacitance associated with circuits, such as metal oxide semiconductor (MOS) integrated circuits, to store signal levels associated with the data to be transferred. These levels are transferred to their intended destination by means of gating devices responsive to clocking signals supplied to the transfer circuitry. One method employing stray capacitance, referred to hereinafter as the precharge method of transfer, involves charging a bus line to a predetermined level when one clocking signal is activated, and then using the logic level of the data to be transferred to either discharge the bus line or to leave the line charged when another clocking signal is activated. Circuits employing this precharge method of transfer are susceptible to undesirable signal level degradations, however, due to unwanted stray capacitance associated with gating devices in the circuit.
Accordingly, it is the principal object of this invention to provide an information transfer bus circuit using the precharge method of transfer which overcomes the signal level degradation resulting from unwanted stray capacitance associated with gating devices in the circuit. Other and incidental objects of this invention will become apparent from a reading of this specification and an inspection of the accompanying drawings.
These objects are accomplished in accordance with the preferred embodiment of the invention by the inclusion of a compensation network in the information transfer bus circuit. This compensation network enhances relevant signal levels in the bus circuit sufficiently to overcome signal level degradation caused by the unwanted stray capacitance associated with gating devices in the circuit. As a result, the chances of erroneous data transfers, due to noise or other factors in the information bus transfer circuit employing the precharge method of transfer, are greatly reduced.